/* * Copyright (C) 2007 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ // #define LOG_NDEBUG 0 #define LOG_TAG "libutils.threads" #include <utils/threads.h> #include <utils/Log.h> #include <cutils/sched_policy.h> #include <cutils/properties.h> #include <stdio.h> #include <stdlib.h> #include <memory.h> #include <errno.h> #include <assert.h> #include <unistd.h> #if defined(HAVE_PTHREADS) # include <pthread.h> # include <sched.h> # include <sys/resource.h> #elif defined(HAVE_WIN32_THREADS) # include <windows.h> # include <stdint.h> # include <process.h> # define HAVE_CREATETHREAD // Cygwin, vs. HAVE__BEGINTHREADEX for MinGW #endif #if defined(HAVE_PRCTL) #include <sys/prctl.h> #endif /* * =========================================================================== * Thread wrappers * =========================================================================== */ using namespace android; // ---------------------------------------------------------------------------- #if defined(HAVE_PTHREADS) // ---------------------------------------------------------------------------- /* * Create and run a new thread. * * We create it "detached", so it cleans up after itself. */ typedef void* (*android_pthread_entry)(void*); static pthread_once_t gDoSchedulingGroupOnce = PTHREAD_ONCE_INIT; static bool gDoSchedulingGroup = true; static void checkDoSchedulingGroup(void) { char buf[PROPERTY_VALUE_MAX]; int len = property_get("debug.sys.noschedgroups", buf, ""); if (len > 0) { int temp; if (sscanf(buf, "%d", &temp) == 1) { gDoSchedulingGroup = temp == 0; } } } struct thread_data_t { thread_func_t entryFunction; void* userData; int priority; char * threadName; // we use this trampoline when we need to set the priority with // nice/setpriority. static int trampoline(const thread_data_t* t) { thread_func_t f = t->entryFunction; void* u = t->userData; int prio = t->priority; char * name = t->threadName; delete t; setpriority(PRIO_PROCESS, 0, prio); pthread_once(&gDoSchedulingGroupOnce, checkDoSchedulingGroup); if (gDoSchedulingGroup) { if (prio >= ANDROID_PRIORITY_BACKGROUND) { set_sched_policy(androidGetTid(), SP_BACKGROUND); } else { set_sched_policy(androidGetTid(), SP_FOREGROUND); } } if (name) { #if defined(HAVE_PRCTL) // Mac OS doesn't have this, and we build libutil for the host too int hasAt = 0; int hasDot = 0; char *s = name; while (*s) { if (*s == '.') hasDot = 1; else if (*s == '@') hasAt = 1; s++; } int len = s - name; if (len < 15 || hasAt || !hasDot) { s = name; } else { s = name + len - 15; } prctl(PR_SET_NAME, (unsigned long) s, 0, 0, 0); #endif free(name); } return f(u); } }; int androidCreateRawThreadEtc(android_thread_func_t entryFunction, void *userData, const char* threadName, int32_t threadPriority, size_t threadStackSize, android_thread_id_t *threadId) { pthread_attr_t attr; pthread_attr_init(&attr); pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED); #ifdef HAVE_ANDROID_OS /* valgrind is rejecting RT-priority create reqs */ if (threadPriority != PRIORITY_DEFAULT || threadName != NULL) { // We could avoid the trampoline if there was a way to get to the // android_thread_id_t (pid) from pthread_t thread_data_t* t = new thread_data_t; t->priority = threadPriority; t->threadName = threadName ? strdup(threadName) : NULL; t->entryFunction = entryFunction; t->userData = userData; entryFunction = (android_thread_func_t)&thread_data_t::trampoline; userData = t; } #endif if (threadStackSize) { pthread_attr_setstacksize(&attr, threadStackSize); } errno = 0; pthread_t thread; int result = pthread_create(&thread, &attr, (android_pthread_entry)entryFunction, userData); if (result != 0) { LOGE("androidCreateRawThreadEtc failed (entry=%p, res=%d, errno=%d)\n" "(android threadPriority=%d)", entryFunction, result, errno, threadPriority); return 0; } if (threadId != NULL) { *threadId = (android_thread_id_t)thread; // XXX: this is not portable } return 1; } android_thread_id_t androidGetThreadId() { return (android_thread_id_t)pthread_self(); } // ---------------------------------------------------------------------------- #elif defined(HAVE_WIN32_THREADS) // ---------------------------------------------------------------------------- /* * Trampoline to make us __stdcall-compliant. * * We're expected to delete "vDetails" when we're done. */ struct threadDetails { int (*func)(void*); void* arg; }; static __stdcall unsigned int threadIntermediary(void* vDetails) { struct threadDetails* pDetails = (struct threadDetails*) vDetails; int result; result = (*(pDetails->func))(pDetails->arg); delete pDetails; LOG(LOG_VERBOSE, "thread", "thread exiting\n"); return (unsigned int) result; } /* * Create and run a new thread. */ static bool doCreateThread(android_thread_func_t fn, void* arg, android_thread_id_t *id) { HANDLE hThread; struct threadDetails* pDetails = new threadDetails; // must be on heap unsigned int thrdaddr; pDetails->func = fn; pDetails->arg = arg; #if defined(HAVE__BEGINTHREADEX) hThread = (HANDLE) _beginthreadex(NULL, 0, threadIntermediary, pDetails, 0, &thrdaddr); if (hThread == 0) #elif defined(HAVE_CREATETHREAD) hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE) threadIntermediary, (void*) pDetails, 0, (DWORD*) &thrdaddr); if (hThread == NULL) #endif { LOG(LOG_WARN, "thread", "WARNING: thread create failed\n"); return false; } #if defined(HAVE_CREATETHREAD) /* close the management handle */ CloseHandle(hThread); #endif if (id != NULL) { *id = (android_thread_id_t)thrdaddr; } return true; } int androidCreateRawThreadEtc(android_thread_func_t fn, void *userData, const char* threadName, int32_t threadPriority, size_t threadStackSize, android_thread_id_t *threadId) { return doCreateThread( fn, userData, threadId); } android_thread_id_t androidGetThreadId() { return (android_thread_id_t)GetCurrentThreadId(); } // ---------------------------------------------------------------------------- #else #error "Threads not supported" #endif // ---------------------------------------------------------------------------- int androidCreateThread(android_thread_func_t fn, void* arg) { return createThreadEtc(fn, arg); } int androidCreateThreadGetID(android_thread_func_t fn, void *arg, android_thread_id_t *id) { return createThreadEtc(fn, arg, "android:unnamed_thread", PRIORITY_DEFAULT, 0, id); } static android_create_thread_fn gCreateThreadFn = androidCreateRawThreadEtc; int androidCreateThreadEtc(android_thread_func_t entryFunction, void *userData, const char* threadName, int32_t threadPriority, size_t threadStackSize, android_thread_id_t *threadId) { return gCreateThreadFn(entryFunction, userData, threadName, threadPriority, threadStackSize, threadId); } void androidSetCreateThreadFunc(android_create_thread_fn func) { gCreateThreadFn = func; } pid_t androidGetTid() { #ifdef HAVE_GETTID return gettid(); #else return getpid(); #endif } int androidSetThreadSchedulingGroup(pid_t tid, int grp) { if (grp > ANDROID_TGROUP_MAX || grp < 0) { return BAD_VALUE; } #if defined(HAVE_PTHREADS) pthread_once(&gDoSchedulingGroupOnce, checkDoSchedulingGroup); if (gDoSchedulingGroup) { if (set_sched_policy(tid, (grp == ANDROID_TGROUP_BG_NONINTERACT) ? SP_BACKGROUND : SP_FOREGROUND)) { return PERMISSION_DENIED; } } #endif return NO_ERROR; } int androidSetThreadPriority(pid_t tid, int pri) { int rc = 0; #if defined(HAVE_PTHREADS) int lasterr = 0; pthread_once(&gDoSchedulingGroupOnce, checkDoSchedulingGroup); if (gDoSchedulingGroup) { if (pri >= ANDROID_PRIORITY_BACKGROUND) { rc = set_sched_policy(tid, SP_BACKGROUND); } else if (getpriority(PRIO_PROCESS, tid) >= ANDROID_PRIORITY_BACKGROUND) { rc = set_sched_policy(tid, SP_FOREGROUND); } } if (rc) { lasterr = errno; } if (setpriority(PRIO_PROCESS, tid, pri) < 0) { rc = INVALID_OPERATION; } else { errno = lasterr; } #endif return rc; } namespace android { /* * =========================================================================== * Mutex class * =========================================================================== */ #if defined(HAVE_PTHREADS) // implemented as inlines in threads.h #elif defined(HAVE_WIN32_THREADS) Mutex::Mutex() { HANDLE hMutex; assert(sizeof(hMutex) == sizeof(mState)); hMutex = CreateMutex(NULL, FALSE, NULL); mState = (void*) hMutex; } Mutex::Mutex(const char* name) { // XXX: name not used for now HANDLE hMutex; assert(sizeof(hMutex) == sizeof(mState)); hMutex = CreateMutex(NULL, FALSE, NULL); mState = (void*) hMutex; } Mutex::Mutex(int type, const char* name) { // XXX: type and name not used for now HANDLE hMutex; assert(sizeof(hMutex) == sizeof(mState)); hMutex = CreateMutex(NULL, FALSE, NULL); mState = (void*) hMutex; } Mutex::~Mutex() { CloseHandle((HANDLE) mState); } status_t Mutex::lock() { DWORD dwWaitResult; dwWaitResult = WaitForSingleObject((HANDLE) mState, INFINITE); return dwWaitResult != WAIT_OBJECT_0 ? -1 : NO_ERROR; } void Mutex::unlock() { if (!ReleaseMutex((HANDLE) mState)) LOG(LOG_WARN, "thread", "WARNING: bad result from unlocking mutex\n"); } status_t Mutex::tryLock() { DWORD dwWaitResult; dwWaitResult = WaitForSingleObject((HANDLE) mState, 0); if (dwWaitResult != WAIT_OBJECT_0 && dwWaitResult != WAIT_TIMEOUT) LOG(LOG_WARN, "thread", "WARNING: bad result from try-locking mutex\n"); return (dwWaitResult == WAIT_OBJECT_0) ? 0 : -1; } #else #error "Somebody forgot to implement threads for this platform." #endif /* * =========================================================================== * Condition class * =========================================================================== */ #if defined(HAVE_PTHREADS) // implemented as inlines in threads.h #elif defined(HAVE_WIN32_THREADS) /* * Windows doesn't have a condition variable solution. It's possible * to create one, but it's easy to get it wrong. For a discussion, and * the origin of this implementation, see: * * http://www.cs.wustl.edu/~schmidt/win32-cv-1.html * * The implementation shown on the page does NOT follow POSIX semantics. * As an optimization they require acquiring the external mutex before * calling signal() and broadcast(), whereas POSIX only requires grabbing * it before calling wait(). The implementation here has been un-optimized * to have the correct behavior. */ typedef struct WinCondition { // Number of waiting threads. int waitersCount; // Serialize access to waitersCount. CRITICAL_SECTION waitersCountLock; // Semaphore used to queue up threads waiting for the condition to // become signaled. HANDLE sema; // An auto-reset event used by the broadcast/signal thread to wait // for all the waiting thread(s) to wake up and be released from // the semaphore. HANDLE waitersDone; // This mutex wouldn't be necessary if we required that the caller // lock the external mutex before calling signal() and broadcast(). // I'm trying to mimic pthread semantics though. HANDLE internalMutex; // Keeps track of whether we were broadcasting or signaling. This // allows us to optimize the code if we're just signaling. bool wasBroadcast; status_t wait(WinCondition* condState, HANDLE hMutex, nsecs_t* abstime) { // Increment the wait count, avoiding race conditions. EnterCriticalSection(&condState->waitersCountLock); condState->waitersCount++; //printf("+++ wait: incr waitersCount to %d (tid=%ld)\n", // condState->waitersCount, getThreadId()); LeaveCriticalSection(&condState->waitersCountLock); DWORD timeout = INFINITE; if (abstime) { nsecs_t reltime = *abstime - systemTime(); if (reltime < 0) reltime = 0; timeout = reltime/1000000; } // Atomically release the external mutex and wait on the semaphore. DWORD res = SignalObjectAndWait(hMutex, condState->sema, timeout, FALSE); //printf("+++ wait: awake (tid=%ld)\n", getThreadId()); // Reacquire lock to avoid race conditions. EnterCriticalSection(&condState->waitersCountLock); // No longer waiting. condState->waitersCount--; // Check to see if we're the last waiter after a broadcast. bool lastWaiter = (condState->wasBroadcast && condState->waitersCount == 0); //printf("+++ wait: lastWaiter=%d (wasBc=%d wc=%d)\n", // lastWaiter, condState->wasBroadcast, condState->waitersCount); LeaveCriticalSection(&condState->waitersCountLock); // If we're the last waiter thread during this particular broadcast // then signal broadcast() that we're all awake. It'll drop the // internal mutex. if (lastWaiter) { // Atomically signal the "waitersDone" event and wait until we // can acquire the internal mutex. We want to do this in one step // because it ensures that everybody is in the mutex FIFO before // any thread has a chance to run. Without it, another thread // could wake up, do work, and hop back in ahead of us. SignalObjectAndWait(condState->waitersDone, condState->internalMutex, INFINITE, FALSE); } else { // Grab the internal mutex. WaitForSingleObject(condState->internalMutex, INFINITE); } // Release the internal and grab the external. ReleaseMutex(condState->internalMutex); WaitForSingleObject(hMutex, INFINITE); return res == WAIT_OBJECT_0 ? NO_ERROR : -1; } } WinCondition; /* * Constructor. Set up the WinCondition stuff. */ Condition::Condition() { WinCondition* condState = new WinCondition; condState->waitersCount = 0; condState->wasBroadcast = false; // semaphore: no security, initial value of 0 condState->sema = CreateSemaphore(NULL, 0, 0x7fffffff, NULL); InitializeCriticalSection(&condState->waitersCountLock); // auto-reset event, not signaled initially condState->waitersDone = CreateEvent(NULL, FALSE, FALSE, NULL); // used so we don't have to lock external mutex on signal/broadcast condState->internalMutex = CreateMutex(NULL, FALSE, NULL); mState = condState; } /* * Destructor. Free Windows resources as well as our allocated storage. */ Condition::~Condition() { WinCondition* condState = (WinCondition*) mState; if (condState != NULL) { CloseHandle(condState->sema); CloseHandle(condState->waitersDone); delete condState; } } status_t Condition::wait(Mutex& mutex) { WinCondition* condState = (WinCondition*) mState; HANDLE hMutex = (HANDLE) mutex.mState; return ((WinCondition*)mState)->wait(condState, hMutex, NULL); } status_t Condition::waitRelative(Mutex& mutex, nsecs_t reltime) { WinCondition* condState = (WinCondition*) mState; HANDLE hMutex = (HANDLE) mutex.mState; nsecs_t absTime = systemTime()+reltime; return ((WinCondition*)mState)->wait(condState, hMutex, &absTime); } /* * Signal the condition variable, allowing one thread to continue. */ void Condition::signal() { WinCondition* condState = (WinCondition*) mState; // Lock the internal mutex. This ensures that we don't clash with // broadcast(). WaitForSingleObject(condState->internalMutex, INFINITE); EnterCriticalSection(&condState->waitersCountLock); bool haveWaiters = (condState->waitersCount > 0); LeaveCriticalSection(&condState->waitersCountLock); // If no waiters, then this is a no-op. Otherwise, knock the semaphore // down a notch. if (haveWaiters) ReleaseSemaphore(condState->sema, 1, 0); // Release internal mutex. ReleaseMutex(condState->internalMutex); } /* * Signal the condition variable, allowing all threads to continue. * * First we have to wake up all threads waiting on the semaphore, then * we wait until all of the threads have actually been woken before * releasing the internal mutex. This ensures that all threads are woken. */ void Condition::broadcast() { WinCondition* condState = (WinCondition*) mState; // Lock the internal mutex. This keeps the guys we're waking up // from getting too far. WaitForSingleObject(condState->internalMutex, INFINITE); EnterCriticalSection(&condState->waitersCountLock); bool haveWaiters = false; if (condState->waitersCount > 0) { haveWaiters = true; condState->wasBroadcast = true; } if (haveWaiters) { // Wake up all the waiters. ReleaseSemaphore(condState->sema, condState->waitersCount, 0); LeaveCriticalSection(&condState->waitersCountLock); // Wait for all awakened threads to acquire the counting semaphore. // The last guy who was waiting sets this. WaitForSingleObject(condState->waitersDone, INFINITE); // Reset wasBroadcast. (No crit section needed because nobody // else can wake up to poke at it.) condState->wasBroadcast = 0; } else { // nothing to do LeaveCriticalSection(&condState->waitersCountLock); } // Release internal mutex. ReleaseMutex(condState->internalMutex); } #else #error "condition variables not supported on this platform" #endif // ---------------------------------------------------------------------------- /* * This is our thread object! */ Thread::Thread(bool canCallJava) : mCanCallJava(canCallJava), mThread(thread_id_t(-1)), mLock("Thread::mLock"), mStatus(NO_ERROR), mExitPending(false), mRunning(false) #ifdef HAVE_ANDROID_OS , mTid(-1) #endif { } Thread::~Thread() { } status_t Thread::readyToRun() { return NO_ERROR; } status_t Thread::run(const char* name, int32_t priority, size_t stack) { Mutex::Autolock _l(mLock); if (mRunning) { // thread already started return INVALID_OPERATION; } // reset status and exitPending to their default value, so we can // try again after an error happened (either below, or in readyToRun()) mStatus = NO_ERROR; mExitPending = false; mThread = thread_id_t(-1); // hold a strong reference on ourself mHoldSelf = this; mRunning = true; bool res; if (mCanCallJava) { res = createThreadEtc(_threadLoop, this, name, priority, stack, &mThread); } else { res = androidCreateRawThreadEtc(_threadLoop, this, name, priority, stack, &mThread); } // The new thread wakes up at _threadLoop, but immediately blocks on mLock if (res == false) { mStatus = UNKNOWN_ERROR; // something happened! mRunning = false; mThread = thread_id_t(-1); mHoldSelf.clear(); // "this" may have gone away after this. return UNKNOWN_ERROR; } // Do not refer to mStatus here: The thread is already running (may, in fact // already have exited with a valid mStatus result). The NO_ERROR indication // here merely indicates successfully starting the thread and does not // imply successful termination/execution. return NO_ERROR; // Exiting scope of mLock is a memory barrier and allows new thread to run } int Thread::_threadLoop(void* user) { Thread* const self = static_cast<Thread*>(user); // force a memory barrier before reading any fields, in particular mHoldSelf { Mutex::Autolock _l(self->mLock); } sp<Thread> strong(self->mHoldSelf); wp<Thread> weak(strong); self->mHoldSelf.clear(); #ifdef HAVE_ANDROID_OS // this is very useful for debugging with gdb self->mTid = gettid(); #endif bool first = true; do { bool result; if (first) { first = false; self->mStatus = self->readyToRun(); result = (self->mStatus == NO_ERROR); if (result && !self->exitPending()) { // Binder threads (and maybe others) rely on threadLoop // running at least once after a successful ::readyToRun() // (unless, of course, the thread has already been asked to exit // at that point). // This is because threads are essentially used like this: // (new ThreadSubclass())->run(); // The caller therefore does not retain a strong reference to // the thread and the thread would simply disappear after the // successful ::readyToRun() call instead of entering the // threadLoop at least once. result = self->threadLoop(); } } else { result = self->threadLoop(); } // establish a scope for mLock { Mutex::Autolock _l(self->mLock); if (result == false || self->mExitPending) { self->mExitPending = true; self->mRunning = false; // clear thread ID so that requestExitAndWait() does not exit if // called by a new thread using the same thread ID as this one. self->mThread = thread_id_t(-1); // note that interested observers blocked in requestExitAndWait are // awoken by broadcast, but blocked on mLock until break exits scope self->mThreadExitedCondition.broadcast(); break; } } // Release our strong reference, to let a chance to the thread // to die a peaceful death. strong.clear(); // And immediately, re-acquire a strong reference for the next loop strong = weak.promote(); } while(strong != 0); return 0; } void Thread::requestExit() { Mutex::Autolock _l(mLock); mExitPending = true; } status_t Thread::requestExitAndWait() { if (mThread == getThreadId()) { LOGW( "Thread (this=%p): don't call waitForExit() from this " "Thread object's thread. It's a guaranteed deadlock!", this); return WOULD_BLOCK; } requestExit(); Mutex::Autolock _l(mLock); while (mRunning == true) { mThreadExitedCondition.wait(mLock); } // This next line is probably not needed any more, but is being left for // historical reference. Note that each interested party will clear flag. mExitPending = false; return mStatus; } bool Thread::exitPending() const { Mutex::Autolock _l(mLock); return mExitPending; } }; // namespace android